Psoriatic arthritis happens in about seven percent of all people who have psoriasis. About a million people in the US have this condition. It occurs in males and females equally. It involves pain, swelling and deformity of the joints affected by the autoimmune response that also happens on the skin. This means that psoriatic arthritis is an autoimmune disease along with psoriasis alone. Males are more likely to have the spondylitic form of the disease (in which the spine is affected), and females are more likely to have the rheumatoid form (in which many joints can be involved). It usually affects individuals between the ages of 35-55 years of age.
Autoimmune diseases are conditions in which the body’s immune system has antibodies and an inflammatory response against its own tissue. There are many types of autoimmune disease and many, like psoriatic arthritis, involve the joints. When you have psoriatic arthritis, you almost always have regular skin psoriasis, too, but in rare cases you can just have psoriatic arthritis. It is usually the really bad cases of psoriasis that are associated with getting psoriatic arthritis.
No one really knows what causes psoriatic arthritis. There are certainly genetic factors which play a role in who gets the disease and who doesn’t. There may be some environmental factors as well, but we don’t know yet what they are. What’s true is that about 40 percent of those with psoriasis or psoriatic arthritis state they have a close relative who also has the condition.